I don't like the idea of printing ££ of PETG just to get to a stage where some other material can be printed, which looking at today's UK market is £££. Seems that even the days of sub £10 ABS are long in the past. I'm expecting that the SecSavr and its sealed enclosure is going to take around 10kg so I'd likely reluctantly get this 10pcs pack for £125. 

It also seems that the seller I found that was selling the PBT pellets has vanished, so even if I got that to work, I'd be back to my long search of finding a supplier. The PET pellets haven't gone anywhere though, so it's an option if I can get around the filament brittleness, considering the working temperature is similar to ABS and so would hopefully survive enclosure temps. 10kg is £28. Throw in £10 worth of masterbatch and it could be a viable solution to keep costs down... well at least for me and those that have a filament extruder.